U.S. patent number 7,848,874 [Application Number 12/207,853] was granted by the patent office on 2010-12-07 for control system and method for starting an engine with port fuel injection and a variable pressure fuel system.
This patent grant is currently assigned to GM Global Technology Operations, Inc.. Invention is credited to Louis A. Avallone, Mark D. Carr, James D. Hay, Jeffrey M. Hutmacher, Jon C. Miller.
United States Patent |
7,848,874 |
Hay , et al. |
December 7, 2010 |
Control system and method for starting an engine with port fuel
injection and a variable pressure fuel system
Abstract
A fuel control system includes a pressure comparison module that
generates a pressure control signal when a fuel supply pressure is
greater than a predetermined pressure value, a temperature
comparison module that generates a temperature control signal when
a temperature of an engine is greater than a predetermined
temperature value, and a pre-crank fuel module that selectively
dispenses pre-crank fuel prior to cranking the engine based on the
pressure control signal and the temperature control signal. A
related fuel control method is also provided.
Inventors: |
Hay; James D. (Milford, MI),
Carr; Mark D. (Fenton, MI), Hutmacher; Jeffrey M.
(Fowlerville, MI), Avallone; Louis A. (Milford, MI),
Miller; Jon C. (Fenton, MI) |
Assignee: |
GM Global Technology Operations,
Inc. (N/A)
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Family
ID: |
40999102 |
Appl.
No.: |
12/207,853 |
Filed: |
September 10, 2008 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20090216425 A1 |
Aug 27, 2009 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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61031392 |
Feb 26, 2008 |
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Current U.S.
Class: |
701/113; 123/491;
123/685 |
Current CPC
Class: |
F02N
99/006 (20130101); F02D 41/065 (20130101); F02D
2200/0602 (20130101) |
Current International
Class: |
G06F
19/00 (20060101); F02M 51/00 (20060101) |
Field of
Search: |
;701/101-103,113
;123/295,305,453,478,491,685 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Kwon; John T
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional Application
No. 61/031,392, filed on Feb. 26, 2008. The disclosure of the above
application is incorporated herein by reference.
Claims
What is claimed is:
1. A fuel control system comprising: a pressure comparison module
that generates a pressure control signal when a fuel supply
pressure is greater than a predetermined pressure value; a
temperature comparison module that generates a temperature control
signal when a temperature of an engine is greater than a
predetermined temperature value; and a pre-crank fuel module that
selectively dispenses pre-crank fuel prior to cranking said engine
based on said pressure control signal and said temperature control
signal.
2. The fuel control system of claim 1 further comprising a fuel
pump, wherein said pre-crank fuel module disables operation of said
fuel pump while said pre-crank fuel is dispensed.
3. The fuel control system of claim 1, wherein said pre-crank fuel
module determines a desired quantity of said pre-crank fuel to
dispense based on at least one of said fuel supply pressure and
said temperature.
4. The fuel control system of claim 1 further comprising a fuel
injector for dispensing said pre-crank fuel, wherein said
temperature is an estimated temperature of said fuel injector.
5. The fuel control system of claim 4, wherein at least one of said
predetermined pressure value and said predetermined temperature
value is based on a voltage supplied to said fuel injector.
6. The fuel control system of claim 4 further comprising a volume
determination module that determines an actual quantity of said
pre-crank fuel dispensed by said fuel injector.
7. The fuel control system of claim 1 further comprising a
plurality of fuel injectors for dispensing fuel to a plurality of
cylinders of said engine, wherein at least one of said plurality of
fuel injectors dispenses said pre-crank fuel.
8. The fuel control system of claim 7, wherein said pre-crank fuel
module pulses a selected number (N) of said plurality of fuel
injectors to dispense said pre-crank fuel based on positions of a
corresponding plurality of intake valves of said engine, where N is
an integer greater than zero.
9. The fuel control system of claim 8 wherein said selected number
(N) of said plurality of fuel injectors corresponds to closed
positions of said plurality of intake valves.
10. The fuel control system of claim 8, wherein said selected
number (N) of said plurality of fuel injectors are simultaneously
pulsed to dispense said pre-crank fuel.
11. A method of fuel control comprising: comparing a fuel supply
pressure and a predetermined pressure value; comparing a
temperature of an engine and a predetermined temperature value; and
dispensing a quantity of pre-crank fuel prior to cranking said
engine based on said pressure comparison and said temperature
comparison.
12. The method of claim 11 further comprising disabling operation
of a fuel pump of said engine during said dispensing said quantity
of pre-crank fuel.
13. The method of claim 11 further comprising determining said
quantity of pre-crank fuel based on at least one of said fuel
supply pressure and said temperature.
14. The method of claim 11, wherein said temperature is an
estimated temperature of a fuel injector of said engine.
15. The method of claim 11 further comprising determining at least
one of said predetermined pressure value and said predetermined
temperature value based on a voltage supplied to a fuel injector of
said engine.
16. A method of fueling an engine comprising: providing a plurality
of fuel injectors for dispensing fuel to said engine; comparing a
pressure of said fuel and a predetermined pressure value; comparing
a temperature of said engine and a predetermined temperature value;
selecting a number (N) of said plurality of fuel injectors based on
positions of a plurality of intake valves of said engine, where N
is an integer greater than zero; and pulsing said N fuel injectors
to dispense a quantity of pre-crank fuel prior to cranking said
engine based on said pressure comparison and said temperature
comparison.
17. The method of claim 16, wherein said number (N) corresponds to
closed positions of said intake valves.
Description
FIELD
The present disclosure relates to engine control systems for
internal combustion engines, and more particularly to control
systems and methods for starting the engines.
BACKGROUND
The statements in this section merely provide background
information related to the present disclosure and may not
constitute prior art.
Internal combustion engines may utilize electronic fuel injection
(EFI) to meter fuel to the engine. Common types of EFI systems
include manifold injection, port injection, pre-combustion chamber
injection, and direct injection. One or more fuel injectors may be
utilized to deliver fuel to the engine. Fuel injectors generally
include a nozzle located at a tip thereof and a valve. The fuel
injectors may be selectively energized to open the valve and
atomize the fuel by pumping the fuel through the tip under
pressure. For example, power may be supplied to a solenoid to open
the valve.
The process of determining and delivering the fuel to the engine at
the appropriate time is known as fuel metering. Fuel metering is
important to controlling an engine's air-fuel ratio to achieve the
desired engine starting and operating performance, emissions,
driveability, and fuel economy.
A period of time that the fuel injectors are energized is referred
to as a pulse width. Typically, the pulse width for each of the
fuel injectors is determined based on a desired quantity (e.g.,
mass) of fuel, the size of the fuel injectors (i.e. fuel flow
capacity), and the pressure of the fuel that will be supplied. To
simplify the determination of the pulse width, some systems assume
that the fuel injectors provide linear fuel flow over the range of
fuel pressures supplied to the fuel injectors. As a practical
matter, fuel injectors are typically capable of linear fuel flow
over a limited range of fuel pressures.
The number and size of the fuel injectors and the fuel pressure
largely depend on the size of the engine and its maximum power
output. However, the maximum fuel pressure that can be used is
limited by the amount of power available to operate the fuel
injectors. The number and size of the fuel injectors is also
dependent on the linear flow range of the fuel injectors.
Engines with large displacement and/or high power output may
require two or more fuel injectors per cylinder. Implementing such
a fuel injection system may require additional engine controllers
to drive the additional fuel injectors. The additional controllers
may require additional packaging space and wiring. Complicated
control methods for turning on and off the additional fuel
injectors to obtain the increased fuel flow may also be required.
The complexity of such a fuel injection system increases the cost
of developing and producing such a system.
SUMMARY
The present disclosure provides a control system and method that
may be used to extend the dynamic flow range of fuel injectors used
to fuel an engine. In one form, the present teachings provide a
fuel control system comprising a pressure comparison module that
generates a pressure control signal when a fuel supply pressure is
greater than a predetermined pressure value, a temperature
comparison module that generates a temperature control signal when
a temperature of an engine is greater than a predetermined
temperature value, and a pre-crank fuel module that selectively
dispenses pre-crank fuel prior to cranking the engine based on the
pressure control signal and the temperature control signal.
In another form, the present teachings provide a method of fuel
control comprising comparing a fuel supply pressure and a
predetermined pressure value, comparing a temperature of an engine
and a predetermined temperature value, and dispensing a quantity of
pre-crank fuel prior to cranking the engine based on the pressure
comparison and the temperature comparison.
In another aspect, the present teachings provide a method of
fueling an engine comprising providing a plurality of fuel
injectors to dispense fuel to the engine, comparing a pressure of
the fuel and a predetermined pressure value, comparing a
temperature of the engine and a predetermined temperature value,
selecting a number (N) of the plurality of fuel injectors based on
positions of a plurality of intake valves of the engine, where N is
an integer greater than zero, and operating the N fuel injectors to
dispense a quantity of pre-crank fuel prior to cranking the engine
based on the pressure comparison and the temperature
comparison.
Further areas of applicability will become apparent from the
description provided herein. It should be understood that the
description and specific examples are intended for purposes of
illustration only and are not intended to limit the scope of the
present disclosure.
DRAWINGS
The drawings described herein are for illustration purposes only
and are not intended to limit the scope of the present disclosure
in any way. The present disclosure will become more fully
understood from the detailed description and the accompanying
drawings, wherein:
FIG. 1 is a functional block diagram of an exemplary powertrain for
a vehicle according to the principles of the present
disclosure;
FIG. 2 is a more detailed functional block diagram of the engine
system shown in FIG. 1;
FIG. 3 is a functional block diagram of a portion of the engine
system shown in FIG. 2;
FIG. 4 is a functional block diagram of an engine control module
according to the principles of the present disclosure;
FIG. 5 is a flow diagram illustrating exemplary steps for a
pre-crank, engine control method according to the principles of the
present disclosure; and
FIG. 6 is a flow diagram illustrating exemplary steps for a
pre-crank, engine control method according to the principles of the
present disclosure.
DETAILED DESCRIPTION
The following description is merely exemplary in nature and is not
intended to limit the present disclosure, application, or uses. As
used herein, the term module, circuit and/or device refers to an
Application Specific Integrated Circuit (ASIC), an electronic
circuit, a processor (shared, dedicated, or group) and memory that
execute one or more software or firmware programs, a combinational
logic circuit, and/or other suitable components that provide the
described functionality.
Exemplary engine control systems and methods are provided herein
that may be used to extend the dynamic flow range of a fuel
injection system used for internal combustion engines. The
principles of the present disclosure may be implemented in a
variable pressure fuel system to enable higher fuel pressures to be
supplied to the fuel injection system while the engine is running.
The control systems and methods of the present disclosure enable
higher running fuel pressures by regulating excessive fuel system
pressure that may develop during periods following the operation of
the engine commonly referred to as "hot soaks." During a hot soak,
auxiliary cooling of the engine is often not provided and heat
within the engine causes temperatures surrounding the engine to
rise above those which exist during the running of the engine. As a
result, the temperature of the fuel in the fuel injection system
may rise, which causes the pressure of the fuel in the fuel
injection system to rise. The elevated pressures that may develop
may exceed the pressure at which the fuel injectors will properly
open during subsequent engine cranking. Accordingly, the control
systems and methods of the present disclosure may be implemented to
reduce the fuel pressures that may develop in the fuel system
during a hot soak and ensure proper starting of the engine.
Referring now to FIG. 1, a functional block diagram of the
powertrain for a vehicle 10 is shown. The vehicle 10 includes an
engine system 12, a transmission 14, and a driveline 16. The engine
system 12 produces driving torque that is transferred through the
transmission 14 to the driveline 16 to drive at least one pair of
wheels (not shown). The engine system 12 includes an internal
combustion engine 18, a fuel system 20, an electrical system 22, an
engine control module (ECM) 24, and an ignition switch 26. The
engine 18 generates driving torque through the combustion of fuel
in the presence of an oxidizer (typically air) in a confined space
referred to as a combustion chamber. The engine 18 may be of
several conventional types commonly used in motorized vehicles. For
example, the engine 18 may be a four-stroke engine, a two-stroke
engine, or a Wankel engine. As discussed herein and shown in the
figures, the engine 18 is a four-stroke engine.
Referring now to FIGS. 2-3, the engine 18 includes an intake
manifold 30, a plurality of cylinders 32, and an exhaust manifold
34. Air is drawn into the intake manifold 30 through a throttle 36
and a mass air flow (MAF) sensor 38. The throttle 36 regulates the
amount of air flow into the intake manifold 30 and may be adjusted
by the ECM 24 based on a commanded engine operating point.
Alternatively, the throttle 36 may be adjusted based on an operator
commanded engine operating point. The MAF sensor 38 is an air flow
meter that generates a mass air flow (MAF) signal that may be used
to determine the rate of air flowing through the MAF sensor 38. The
MAF signal is communicated to the ECM 24, which determines the air
flow rate based on the MAF signal.
The intake manifold 30 may include a plurality of intake runners 39
for delivering air within the intake manifold 30 to the cylinders
32. Air entering the intake manifold 30 is distributed among the
intake runners 39 and is delivered to the cylinders 32 via a
plurality of intake ports 40. The flow of air from the intake ports
40 into the cylinders 32 is controlled by a plurality of intake
valves 42. The intake valves 42 sequentially open to allow air into
the cylinders 32 and close to inhibit the flow of air into the
cylinders 32.
Air in the cylinders 32 is mixed with fuel and the air and fuel
mixture is combusted within the cylinders 32 to drive a plurality
of piston assemblies 44. A plurality of spark plugs 46 are located
within the cylinders 32 to provide the energy necessary to initiate
the combustion process. The piston assemblies 44 are connected to a
crankshaft 48 that rotates in response to the movement of the
piston assemblies 44. The crankshaft 48 rotates at engine speed or
at a rotational rate that is proportional to engine speed.
A crankshaft position sensor 50 may be utilized to sense the
position of the crankshaft 48. The crankshaft position sensor 50
may generate a crankshaft position (CPS) signal that may be used to
determine the position and rotational speed of the crankshaft 48.
The CPS signal may be communicated to the ECM 24, which may
determine the position of the crankshaft 48 and the rotational
speed of the engine 18 based on the CPS signal.
Combusted air within the cylinders 32 is selectively pumped into
the exhaust manifold 34 via a plurality of exhaust ports 52 by the
piston assemblies 44. The flow of air from the cylinders 32 into
the exhaust manifold 34 is controlled by a plurality of exhaust
valves 54. Specifically, the exhaust valves 54 sequentially open to
allow air to exit the cylinders 32 and close to inhibit air from
exiting the cylinders 32. A portion of the exhaust gas within the
exhaust manifold 34 may be routed back to the intake manifold 30
via an exhaust gas recirculation (EGR) valve assembly 55. The EGR
valve assembly 55 may generate an EGR signal that may be used to
determine the amount of exhaust gas recirculation. The EGR signal
may be communicated to the ECM 24, which may determine the amount
of exhaust gas recirculation based on the EGR signal.
The timing and duration of the opening and closing of the intake
and exhaust valves 42, 54 during the operation of the engine 18 may
be controlled by a plurality of camshafts 56. The camshafts 56 may
have a plurality of lobes 58, 60 engaged with the intake and
exhaust valves 42, 54, respectively, to control their operation.
The camshafts 56 may be connected to the crankshaft 48 to rotate at
a speed proportional to the rotational speed of the crankshaft 48,
typically one-half the speed of the crankshaft 48. While two
camshafts 56 are illustrated (FIG. 3), a single camshaft having
lobes 58, 60 may be provided. It is also contemplated that any
other suitable device for selectively operating the intake and
exhaust valves 42, 54 may be provided.
The number of cylinders 32 and, thus intake and exhaust ports 40,
52, associated with the engine 18 may vary. For example, the engine
18 may have 4, 5, 6, 10, 12 and 16 cylinders. As discussed herein,
the engine 18 has eight cylinders, eight intake ports 40, and eight
exhaust ports 52 (FIG. 2). The number of intake and exhaust valves
42, 54 may also vary. Specifically, the number of intake and
exhaust valves 42, 54 associated with each of the cylinders 32 may
be one or more. As discussed herein, each of the cylinders 32 has
corresponding intake and exhaust valves 42, 54 (FIG. 2).
The engine 18 further includes an electric starter 62 coupled to
the crankshaft 48. The starter 62 is selectively operable to rotate
the crankshaft 48 as may be desired to crank, and thereby start the
engine 18.
Heat generated during the operation of the engine 18 may be
absorbed by coolant (not shown) flowing through the engine 18 and
dissipated by an engine cooling system (also not shown). A coolant
temperature sensor 64 may be located in the engine 18 to sense the
temperature of the coolant and to generate an engine coolant
temperature sensor (ECT) signal. The ECT signal may be used to
determine a temperature of the engine 18. The ECT signal may be
communicated to the ECM 24, which may determine the temperature of
the engine 18 based on the ECT signal.
The engine 18 is lubricated by oil (not shown) that flows through
portions of the engine 18. An oil temperature sensor 66 may be
located in the engine 18 to sense the temperature of the oil and to
generate an oil temperature sensor (OT) signal that may be used to
determine the temperature of the oil. The OT signal may be
communicated to the ECM 24, which may determine the temperature of
the oil based on the OT signal.
Referring still to FIGS. 2-3, the fuel system 20 is selectively
operable to deliver a specified quantity of fuel (e.g., gasoline,
diesel, ethanol) to the engine 18. The fuel system 20 may include a
fuel tank assembly 70 that supplies fuel at a desired pressure to a
fuel rail assembly 72 via a fuel supply line 74. The fuel system 20
may further include a fuel system control module 76.
The fuel tank assembly 70 may include a fuel pump 78 fluidly
coupled to the fuel supply line 74. The fuel pump 78 may be an
electrically-controlled, variable speed fuel pump operable to
supply fuel at a desired pressure to the fuel supply line 74. The
fuel tank assembly 70 may further include a fuel pressure sensor 80
located at an outlet of the fuel pump 78 proximate the fuel supply
line 74 that generates a fuel pressure (FPS) signal. The FPS signal
may be communicated to the fuel system control module 76 (see FIG.
3), which may determine a pressure of the fuel supplied by the fuel
pump 78 to the supply line 74 (P.sub.supply) based on the FPS
signal.
The fuel system control module 76 may communicate the pressure of
the fuel in the supply line 74 (P.sub.supply) to the ECM 24. The
fuel system control module 76 may also control the speed of the
fuel pump 78 based on the FPS signal generated by the fuel pressure
sensor 80. For example, the fuel system control module 76 may
receive a desired fuel pressure signal (P.sub.desired) from the ECM
24 and may control the speed of the fuel pump 78 to achieve the
desired fuel pressure (P.sub.desired) in the supply line 74.
The desired fuel pressure (P.sub.desired) may vary based on the
engine operating point. For example, the fuel system control module
76 may control the speed of the fuel pump 78 to operate at a first
desired fuel pressure during periods when the engine is operated
under low power demand. The fuel system control module 76 may
further control the speed of the fuel pump 78 to operate at a
second desired fuel pressure greater than the first desired fuel
pressure during periods when the engine is operated under high
power demand.
The fuel rail assembly 72 may selectively deliver a quantity of
fuel to the intake manifold 30. The fuel rail assembly may include
a plurality of electronic fuel injectors 82 fluidly coupled to a
pair of fuel rails 84. The fuel rail assembly 72 may further
include a cross-over pipe 86 disposed between the fuel rails 84 to
fluidly couple the fuel rails 84.
The number of fuel injectors 82 may vary. As discussed herein,
eight fuel injectors 82 are provided. The fuel injectors 82 are
selectively operable to deliver a predetermined quantity of fuel to
the intake manifold 30. Each of the fuel injectors 82 may be
located at a corresponding one of the intake runners 39 (FIG. 2) to
dispense fuel within the intake runners 39 and thereby provide fuel
to a corresponding one of the cylinders 32. The fuel injectors 82
may be of any conventional type.
The fuel rails 84 may be fluidly coupled to the fuel supply line 74
to supply pressurized fuel supplied by the fuel tank assembly 70 to
the fuel injectors 82. While a pair of fuel rails 84 is shown, a
single fuel rail may be provided.
With particular reference to FIG. 2, the electrical system 22
provides power to operate the various electrical components
associated with the vehicle 10 and may be of any conventional type.
For example, the electrical system 22 may include a battery 90 for
providing power to the vehicle 10 when the engine 18 is not running
or is being started. The electrical system 22 may further include
an alternator 92 drivingly coupled to the engine 18 for providing
additional power to the vehicle 10 and recharging the battery 90
while the engine is running.
Referring now to FIGS. 2-4, the ECM 24 will now be described in
detail. The ECM 24 may control the starting and operation of the
engine 18. To this end, the ECM 24 may receive and process signals
from the ignition switch 26, the engine 18, the fuel system 20, and
the electrical system 22. Based on the signals it receives, the ECM
24 may generate timed engine system control commands that are
output to the engine 18, the fuel system 20, and the electrical
system 22. Specifically, the ECM 24 may receive signals from the
engine 18 including, but not limited to, the CPS, EGR, ECT, MAF,
and OT signals (hereinafter "engine signals"). The ECM 24 may
receive signals from the fuel system 20 including, but not limited
to, the FPS signal (hereinafter "fuel system signals"). The ECM 24
may also receive an ignition (IGN) signal generated by the ignition
switch 26.
The ECM 24 may store one or more of the engine and fuel system
signals in memory for a period of time so that they may be
retrieved for subsequent determinations by the ECM 24. Based on the
IGN signal, the engine signals, and the fuel system signals, the
ECM 24 may generate timed engine and fuel system control commands
including, but not limited to, signals that control the throttle
36, the spark plugs 46, the starter 62, the fuel system control
module 76, and the fuel injectors 82.
With particular reference to FIG. 4, the ECM 24 may include a
pre-crank control module 100, a fuel control module 102, an
injector control module 104, a timed command module 106, and a
starter module 108. The pre-crank control module 100 may include a
pressure comparison module 110, a temperature comparison module
112, and a pre-crank dispensing module 114.
The pressure comparison module 110 may receive the pressure of the
fuel in the fuel supply line 74 (P.sub.supply) from the fuel system
control module 76. Based on P.sub.supply, the pressure comparison
module may determine an estimated pressure (P.sub.fuel) of the fuel
supplied to the fuel injectors 82. The pressure comparison module
110 may also generate a pressure control signal (CS1) based on a
comparison of P.sub.fuel and a threshold pressure value
(P.sub.threshold). The pressure comparison module 110 may generate
CS1 to indicate whether P.sub.fuel is greater than P.sub.threshold.
The pressure comparison module 110 may output CS1 to the pre-crank
dispensing module 114.
The temperature comparison module 112 may receive one or more
engine signals and generate a temperature control signal (CS2)
based on the signals it receives. For exemplary purposes, the
temperature comparison module 112 may receive the IGN, ECT, OT,
EGR, and MAF signals (FIG. 4). Based on the signals it receives,
the temperature comparison module 112 may determine a temperature
of the engine (T.sub.eng) and generate CS2 by comparing T.sub.eng
to a threshold temperature value (T.sub.threshold). The temperature
comparison module 112 may generate CS2 to indicate whether
T.sub.eng is greater than T.sub.threshold. The temperature
comparison module 112 may output CS2 to the pre-crank dispensing
module 114.
The pre-crank dispensing module 114 may receive CS1, CS2, and one
or more engine and fuel system signals. Based on these signals, the
pre-crank dispensing module 114 may generate a starter control
signal (CS3) for controlling the starter 62 and a pre-crank fuel
control signal (CS4) for controlling pre-crank operation of the
fuel injectors 82. For example, the pre-crank dispensing module 114
may generate CS4 to indicate a desired quantity of fuel
(m.sub.fuel) to deliver to the engine 18 prior to cranking. The
pre-crank dispensing module 114 may receive the IGN, CS1, CS2, and
CPS signals for generating CS3 and CS4 (FIG. 4). The pre-crank
dispensing module 114 may output CS3 to the starter module 108 and
the timed command module 106. The pre-crank dispensing module 114
may output CS4 to the timed command module 106.
The pre-crank control module 100 may further include a dispensed
volume determination module 116 for determining the total quantity
of fuel delivered during pre-crank operation of the fuel injectors
82. The dispensed volume determination module 116 may receive a
fuel system control command signal from the timed command module
106 and the pressure of the fuel in the fuel supply line 74
(P.sub.supply) from the fuel system control module 76. Based on
these signals, the dispensed volume determination module 116 may
determine a total quantity of fuel (m.sub.actual) delivered to the
engine 18 prior to cranking. The dispensed volume determination
module may output m.sub.actual to the fuel control module 102.
The fuel control module 102 may determine a desired quantity of
fuel (m.sub.desired) to deliver to the engine 18 to operate the
engine 18 at a desired engine operating point (e.g., power output).
The fuel control module 102 may receive the IGN signal from the
ignition switch 26, m.sub.actual from the dispensed volume
determination module 116, an air-per-cylinder (APC) value, and an
air-fuel ratio (A/F) value (FIG. 4). The fuel control module 102
may determine m.sub.desired based on the IGN signal and the
m.sub.actual, APC, and A/F values it receives. The APC and A/F
values may be determined based on the desired engine operating
point. The fuel control module 102 may output m.sub.desired to the
injector control module 104.
The injector control module 104 may receive m.sub.desired from the
fuel control module 102 and the CPS signal from the crankshaft
position sensor 50. Based on m.sub.desired and the CPS signal it
receives, the injector control module 104 generates an injector
control signal (CS5) for selectively operating the fuel injectors
82. Specifically, the injector control module 104 may determine the
quantity of fuel to be delivered by the fuel injectors 82 to
deliver the desired quantity of fuel (m.sub.desired). The injector
control module 104 may output CS5 to the timed command module
106.
The timed command module 106 may generate timed engine and fuel
system control command signals used to operate the engine system 12
and the fuel system 20. The timed engine and fuel system control
commands include, but are not limited to a commanded fuel pressure
signal (P.sub.command) for controlling the fuel system control
module 76, a commanded throttle signal (THROTTLE) for controlling
the throttle 36, a commanded spark signal (SPARK) for controlling
the spark plugs 46, and a commanded fuel signal (FUEL) for
controlling the fuel injectors 82. The timed command module 106 may
generate P.sub.command, THROTTLE, SPARK, and FUEL based on the CPS
signal, CS3, CS4, CS5, P.sub.desired, and APC.
The starter module 108 may receive CS3 from the pre-crank
dispensing module 114 and the IGN signal from the ignition switch
26 and generate a starter signal (START) for selectively operating
the starter 62. As discussed in more detail below, the starter
module 108 may generate the starter command signal (START) to
inhibit the operation of the starter 62 based on CS3.
The ignition switch 26 may be a three position switch of any known
type and have "OFF", "ON", and "CRANK" positions. The Ignition
switch 26 may be selectively moved between the "CRANK", "ON", and
"OFF" positions to cause the ECM 24 to start, run, and stop the
engine 18, respectively. The ignition switch 26 may generate the
IGN signal based on a position of the ignition switch in the "OFF",
"ON", or "CRANK" positions.
Referring now to FIG. 5, an exemplary pre-crank, engine control
method 200 according to the present disclosure is provided and will
now be described. The engine control method 200 may be implemented
as a computer program stored in the memory of the ECM 24 and run
every key cycle at a time when a desired set of entry conditions
exist. As used herein, the term key cycle generally refers to an
ignition switch cycle which begins when the ignition switch 26
moves from the OFF position into the ON or CRANK position and ends
when the ignition switch 26 has moved from the ON or CRANK
positions back to the OFF position.
The decision to run the engine control method 200 may be made by
the ECM 24 based on the operating conditions existing on either the
current key cycle or prior key cycles as will be explained in
further detail below. The engine control method 200 is a pre-crank
control method. Thus, the engine control method 200 may be
implemented to supplement other scheduled control methods for
generating timed engine and fuel system control commands during
engine cranking.
The engine control method 200 may run one or more times each key
cycle prior to the regular cranking operation of the engine 18.
Where the control method 200 has already run during the current key
cycle, control under the control method 200 may be inhibited until
the engine 18 has been running for a predetermined time period. The
control method 200 may be inhibited in the foregoing manner during
the current key cycle and/or subsequent key cycles until the engine
18 has run for the predetermined time period. For simplicity, the
engine control method 200, as discussed herein and shown in the
figures, is a supplementary control method that runs once every key
cycle prior to the regular cranking operation of the engine 18.
The engine control method 200 begins in step 202. In step 202, the
ECM 24 determines whether a set of entry conditions are satisfied.
The entry conditions will generally be satisfied at a time when the
ignition switch 26 has just moved into the CRANK position from the
OFF position. The entry conditions may also include whether the
engine control method 200 has already run during the current key
cycle and whether there are other overriding reasons to inhibit
control under the engine control method 200. For example,
diagnostic control methods implemented with the ECM 24 to monitor
the operation of the engine and fuel systems 12, 20 may provide an
overriding reason to inhibit control under the engine control
method 200.
For simplicity, in step 202, the ECM 24 determines whether the
ignition switch 26 has just moved into the CRANK position from the
OFF position. If the ignition switch 26 has just moved into the
CRANK position from the OFF position, then control proceeds in step
204, otherwise control under the engine control method 200 ends and
control is transferred to other regularly scheduled engine control
methods (e.g., engine cranking).
In step 204, the pressure comparison module 110 determines the
estimated pressure (P.sub.fuel) of the fuel supplied to the fuel
injectors 82 based on the value of P.sub.supply determined by the
fuel system control module 76. The estimated pressure (P.sub.fuel)
of the fuel supplied to the fuel injectors 82 may be determined in
a variety of ways to account for the particular configuration of
the fuel system 20. As discussed herein, the pressure comparison
module 110 determines P.sub.fuel by equating P.sub.fuel to the
pressure of the fuel in the fuel supply line 74 (P.sub.supply).
Next in step 206, the temperature comparison module 112 determines
the estimated temperature (T.sub.eng) of the engine 18 based on the
ECT signal generated by the coolant temperature sensor 64. The
estimated engine temperature (T.sub.eng) may be determined in a
variety of ways and may represent an estimated temperature of
certain components of the engine 18. For example T.sub.eng may be
an estimated temperature of the coolant within the engine 18 or an
estimated temperature of the intake valves 42. As discussed herein,
T.sub.eng is an estimated temperature of the fuel injectors 82.
More specifically, T.sub.eng is an estimated temperature of the
spray tips of the fuel injectors 82.
To this end, the temperature comparison module 112 may implement a
temperature model for determining T.sub.eng based on, but not
limited to, engine coolant temperature (e.g., ECT signal), intake
manifold air temperature (MAT), engine airflow (e.g. MAF signal),
engine oil temperature (OT), and exhaust gas recirculation mass
flow (EGR). Thus, the temperature comparison module 112 may
determine T.sub.eng using a temperature model that may be generally
represented by the general equation: T.sub.eng=f(ECT, MAT, MAF, OT,
and EGR).
Alternatively, the temperature comparison module 112 may look up
the value of T.sub.eng in memory tables stored within the memory of
the ECM 24, based on the foregoing engine signals. The temperature
model or memory tables may be developed by empirical methods using
quasi-steady-state engine testing. During such engine testing, the
engine operating conditions may be varied and the resulting
temperature of the fuel injectors measured. For exemplary purposes,
the temperature comparison module 112 determines T.sub.eng in step
206 using a temperature model and the ECT, MAT, MAF, OT and EGR
signals.
In step 208, the pressure comparison module 110 obtains the
pressure threshold (P.sub.threshold) value from memory and compares
the value of P.sub.fuel determined in step 204 and P.sub.threshold.
Based on the comparison of P.sub.fuel and P.sub.threshold, the
pressure comparison module 110 may generate the pressure control
signal (CS1) to indicate whether P.sub.fuel is greater than
P.sub.threshold. If P.sub.fuel is greater than P.sub.threshold then
control proceeds in step 210. If P.sub.fuel is less than or equal
to P.sub.threshold, then control under the engine control method
200 ends.
The value of P.sub.threshold may generally relate to the fuel
pressure above which the fuel injectors 82 may not properly open
under anticipated operating conditions (e.g., T.sub.eng and voltage
available to the fuel injectors) during subsequent engine cranking.
P.sub.threshold may be a predetermined value based on
quasi-steady-state testing of the fuel injectors 82. During such
testing, fuel injector performance may be measured under varying
operating conditions including fuel injector temperature, fuel
pressure, voltage, and pulse width. Thus, the pressure threshold
P.sub.threshold may be a predetermined value that is stored in
memory. Alternatively, a table of values for P.sub.threshold may be
stored in memory and P.sub.threshold may be looked up in the tables
based on the value of T.sub.eng determined in step 206. For
exemplary purposes, P.sub.threshold a predetermined value equal to
about 400 kPa that is retrieved from memory in step 206.
In step 210, the temperature comparison module 112 obtains the
temperature threshold (T.sub.threshold) value from memory and
compares the value of T.sub.eng determined in step 206 and
T.sub.threshold. Based on the comparison of T.sub.eng and
T.sub.threshold, the temperature comparison module 112 may generate
the temperature control signal (CS2) to indicate whether T.sub.eng
is greater than T.sub.threshold. If T.sub.eng is greater than
T.sub.threshold, then control proceeds in step 212, otherwise
control under the engine control method 200 ends.
The value of T.sub.eng obtained in step 210 may generally relate to
a temperature of the engine above which the fuel injectors 82 may
not properly open under the anticipated operating conditions (e.g.,
P.sub.fuel and voltage available to the fuel injectors) during
subsequent engine cranking. Thus, T.sub.threshold may be a single
predetermined value that is obtained from memory. Alternatively,
T.sub.threshold may be obtained from a table of values stored in a
memory using the value of P.sub.fuel determined in step 204. For
exemplary purposes, T.sub.threshold is a predetermined value equal
to about 30.degree. C. that is retrieved from memory in step
210.
In step 212, the pre-crank dispensing module 114 determines the
parameters for operating selected fuel injectors prior to cranking
the engine 18. Specifically, in step 212 the pre-crank dispensing
module determines a desired quantity of fuel (m.sub.fuel) to
deliver to the engine 18. The pre-crank dispensing module 114 also
determines a selected number (N) of the fuel injectors 82 and
corresponding pulse widths (pw.sub.N) for each of the N fuel
injectors 82 in order to deliver the desired quantity of fuel
(m.sub.fuel). The desired quantity of fuel (m.sub.fuel) may
generally relate to a quantity of fuel that may be dispensed prior
to cranking the engine 18 to achieve a desired reduction in the
pressure of the fuel supplied to the fuel injectors 82 (i.e.,
P.sub.fuel). The desired quantity of fuel (m.sub.fuel) may also
relate to a quantity of fuel that may be dispensed prior to
cranking the engine 18 without significantly degrading the starting
performance of the engine 18.
The desired quantity of fuel (m.sub.fuel), the selected number (N)
of the fuel injectors 82, and the pulse widths (pw.sub.N) may be
predetermined values that are stored in memory for retrieval by the
pre-crank dispensing module 114 in step 212. The values of
m.sub.fuel, N, and pw.sub.N may be predetermined based on engine
development testing. For example, the number and selection of the
fuel injectors (i.e., N) and the quantity of fuel delivered prior
to cranking the engine (i.e., m.sub.fuel) may be varied during
engine starting testing and the resulting reduction in the pressure
of the fuel supplied to the fuel injectors and engine starting
performance may be measured and evaluated. Alternatively,
m.sub.fuel, N, and pw.sub.N may be determined using a simple
calculation based on the estimated pressure (P.sub.fuel) determined
in step 204, the estimated engine temperature (T.sub.eng)
determined in step 206, and a voltage supplied to the injectors by
the electrical system 22.
It also may be desired to determine the N fuel injectors 82 by
determining which fuel injectors correspond to the cylinders that
have closed intake valves at the time when control arrives in step
212. Accordingly, the N fuel injectors 82 may be determined based
on positions of the intake valves 42. Specifically, the pre-crank
dispensing module 114 may determine the N fuel injectors 82 to
correspond to the cylinders 32 with closed intake valves 42 based
on the CPS signal generated by the crankshaft position sensor
50.
The pre-crank dispensing module 114 may use the CPS signal
generated at the time in which control arrives in step 212 during
the current key cycle. Alternatively, the pre-crank dispensing
module 114 may use a timed segment of the CPS signal stored in
memory that corresponds to the time the engine 18 stopped on the
last key cycle. The positions of the intake valves 42 also may be
determined based on the position of the camshafts 56.
For exemplary purposes, in step 212, the pre-crank dispensing
module 114 determines the N fuel injectors 82 to correspond to the
cylinders 32 having intake valves 42 which are closed.
Specifically, the pre-crank dispensing module 114 determines the N
fuel injectors 82 by evaluating the timed segment of the CPS signal
stored in memory during the last key cycle. The corresponding pulse
widths (pw.sub.N) for each of the N fuel injectors 82 are each
predetermined values equal to about 4 milliseconds. Thus, in step
212, the pre-crank dispensing module 114 retrieves the pulse widths
(pw.sub.N) from memory. The pre-crank dispensing model generates
CS4 to indicate the N fuel injectors 82 and the corresponding pulse
widths (pw.sub.N).
In step 214, the timed command module 106 generates the timed
pressure command signal (P.sub.command) to inhibit the operation of
the fuel pump 78 during the pre-crank operation of the N fuel
injectors 82. The timed command module 106 may generate
P.sub.command based on the control signals CS3 and CS4 generated by
the pre-crank dispensing module 114.
In step 216, the timed command module 106 generates a timed fuel
system control command signal (FUEL) to selectively pulse the fuel
injectors 82 based on the fuel control signal (CS4) generated by
the pre-crank dispensing module 114 in step 212. Specifically, the
timed command module 106 generates the FUEL signal to pulse the N
fuel injectors 82 for the corresponding pulse widths (pw.sub.N) to
deliver the desired quantity of fuel (m.sub.fuel) to the engine 18
prior to cranking the engine. The FUEL signal may pulse the fuel
injectors 82 simultaneously, sequentially, or in a random manner.
As discussed herein, the timed command module generates the FUEL
signal in step 216 to pulse the fuel injectors 82
simultaneously.
Control under the engine control method 200 ends in step 216 and
control is transferred to other regularly scheduled engine control
methods (e.g. engine cranking) stored within the memory of the ECM
24.
In the foregoing manner, the engine control method 200 may be used
to extend the dynamic flow range of the fuel injectors 82. By
inhibiting the operation of the fuel pump 78 and pulsing the
selected number (N) of the fuel injectors 82 prior to energizing
the starter 62, the engine control method 200 uses the increased
voltage that is available prior to cranking the engine 18 to
operate the fuel injectors 82 at elevated fuel rail pressures. In
turn, operating the fuel injectors 82 prior to cranking the engine
18 reduces the pressure of the fuel in the fuel rails 84, enabling
the fuel injectors 82 to operate properly during subsequent
cranking and starting of the engine 18. Depending on the quantity
of fuel delivered prior to cranking the engine 18, one or more of
the normally scheduled pulses of the fuel injectors 82 may be
inhibited during subsequent cranking to avoid over fueling the
engine 18.
Referring now to FIG. 6, another engine control method 230
according to the principles of the present disclosure is provided.
In view of the substantial similarity between engine control method
200 and engine control method 230, like reference numerals will be
used hereinafter and in the drawings to identify like steps. New
reference numerals will be introduced to identify steps that or new
or have been modified. For brevity, those steps that are new or
have been modified will be described in detail.
The engine control method 230 includes steps 202 through 216 of
engine control method 200, along with additional steps 232 and 234.
The engine control method 230 begins in step 202 and proceeds
through step 216 as previously described. From step 216, control
proceeds in step 232.
In step 232, the dispensed volume determination module 116
determines the average fuel pressure (P.sub.ave,N) supplied to the
N fuel injectors 82 pulsed in step 216. The dispensed volume
determination module 116 may determine P.sub.ave,N based on
P.sub.supply and the FUEL signal. For example, in step 232 the
dispensed volume determination module 116 may determine P.sub.ave,N
for each of the N fuel injectors 82 using the values of
P.sub.supply generated during the operation of the fuel injectors
82 in step 216.
Since the FUEL signal generated in step 216 simultaneously pulses
the fuel injectors 82, the value of P.sub.ave,N for each of the N
fuel injectors 82 determined in step 232 may be equal. In
alternative implementations of the present disclosure in which the
fuel injectors are not pulsed simultaneously, P.sub.ave,N may vary
for each of the N fuel injectors 82. The average fuel pressure
(P.sub.ave,N) may vary due to incremental reductions in the fuel
pressure that may result from pulsing the N fuel injectors 82
sequentially or randomly.
In step 234, the dispensed volume determination module 116
determines an actual total quantity of fuel (m.sub.actual)
dispensed by the N fuel injectors 82 pulsed in step 216. The
dispensed volume determination module 116 may determine
m.sub.actual based on the values determined for P.sub.ave,N in step
232. For example, m.sub.actual may be calculated using the
following formula: m.sub.actual=.SIGMA.pw.sub.N.times.C.sub.N,
where C.sub.N represents the fuel flow capacity (e.g. lb/hr) of
each of the N fuel injectors 82 at P.sub.ave,N. It will be
appreciated that the value of m.sub.actual determined in step 234
will generally be equal to the desired quantity of fuel
(m.sub.fuel) determined in step 212. The value of m.sub.actual
determined in step 234 may be stored in the memory (e.g.,
non-volatile memory) and used by other engine control methods for
cranking and starting the engine 18. As one example, the value of
m.sub.fuel may be used to determine the desired quantity of fuel
(e.g., m.sub.desired) to deliver during subsequent cranking,
starting, and operation of the engine 18 to avoid over fueling the
engine 18.
Control under the engine control method 230 ends in step 234 and
control is transferred to other regularly scheduled engine control
methods (e.g. engine cranking) stored within the memory of the ECM
24.
In the foregoing manner, the engine control method 230 may be used
to extend the dynamic flow range of the fuel injectors 82 and
provide pre-crank fueling information that may be used by other
scheduled engine control methods to compensate for fuel delivered
to the engine prior to engine cranking.
Those skilled in the art may now appreciate from the foregoing
description that the broad teachings of the present disclosure may
be implemented in a variety of forms. Therefore, while this
disclosure includes particular examples, the true scope of the
disclosure should not be so limited, since other modifications will
become apparent to the skilled practitioner upon a study of the
drawings, the specification and the following claims.
* * * * *